ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04043.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04044.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04045.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04046.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryExercise induced pulmonary haemorrhage (EIPH) is a serious problem in the Thoroughbred industry. The condition apparently occurs essentially in all Thoroughbreds in training but the mechanism has proved elusive. There is now strong evidence that the condition is caused by mechanical failure of the walls of the pulmonary capillaries when the pressure inside them rises to very high levels. It is well known that pulmonary capillaries have extremely thin walls to allow rapid exchange of respiratory gases across them. Recently we have shown that the wall stresses are very large when the capillary transmural pressure is raised, and in anesthetised rabbits, ultrastructural damage to the walls is seen at pressures of 40 mmHg and above. The incidence of stress failure is greatly increased at high lung volumes; and many of the ultrastructural changes are rapidly reversible when the capillary pressure is reduced. The principal forces acting on the capillary have been analysed. The strength of the thin part of the capillary wall can be attributed to theType IVcollagen in the extracellular matrix. The pulmonary vascular pressures of galloping Thoroughbreds reach very high levels. Mean pulmonary artery and left atrial pressures of up to 120 and 70 mmHg respectively have been directly measured with indwelling catheters. The reason for the high pulmonary vascular pressures is that these animals have been selectively bred over hundreds of years to run at great speeds over short distances and their maximal oxygen consumptions are very high. As a consequence, cardiac outputs are substantial, and the left ventricle needs very high filling pressures. Ultrastructural studies of Thoroughbred lungs after galloping show the typical changes of stress failure of capillaries. Calculations of capillary wall stress from measurements of the radius of the capillaries and the thickness of the wall confirm that the stresses are very high. The fact that the lesions of EIPH are most commonly seen initially in the dorso caudal region of the lung appears to argue against the stress failure hypothesis. However, it is known that resting blood flow is particularly high to that region and it may also be that the alveolar pressure falls transiently to very low levels or that the alveoli in that region are overexpanded. All these factors could increase capillary wall stress. There is evidence that frusemide reduces pulmonary vascular pressures during galloping. However, the blood gas barrier needs to be extremely thin for gas exchange, but immensely strong to withstand the capillary wall stresses. Thoroughbreds fail on both counts. First they develop arterial hypoxaemia as a result of diffusion limited oxygen transfer in the lung during galloping and, therefore, they cannot afford to have thicker blood‐gas barriers. On the other hand, their capillary walls are not strong enough to withstand the substantial wall stresses that develop as a result of the high capillary pressures. Therefore, to some extent, EIPH is an inevitable consequence of the extremely high cardiac outputs required by these elite athlete

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04047.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryHistopathology was compared to culture results and cytology from horses with corneal stromal abscess at the Auburn University and the Ohio State University Veterinary Teaching Hospitals. Significant bacteria were not isolated in culture or seen on histopathology in any of the horses. Although most bacteria infecting equine corneas can be isolated with blood and MacConkey's agars, failure to detect bacterial growth may not rule out infection because anaerobic or intracellular bacteria would not be isolated. The inability to visualise bacterial organisms on histological sections did not rule out their presence in the tissue, because there is often destruction of bacteria by neutrophils, macrophages and antibiotic therapy greatly reducing their numbers. Fungal keratitis was diagnosed by histopathology in 4 of 11 eyes (36%) and keratitis with no aetiological agent in 7 of 11 eyes (64%). Nine of 11 horses (82%) had a prominent neutrophilic stromal infiltrate and 2 (18%) had a predominately pyogranulomatous reaction. Two of the 4 lesions that showed histological evidence of fungal infection were positive for identifiable fungi on culture and cytology. Fungal cultures of the other 2 cases with histological evidence of mycotic keratitis were negative or grew unidentifiable fungi which were considered pathogenic because, on histopathological sections, fungal hyphae were found deep in the corneal stroma surrounded by an inflammatory reaction. In 3 of 6 cases where fungi were recovered on culture, they were considered contaminants based on lack of evidence of organisms in histopathological sections. Histopathology and the use of special stains were important in the interpretation of culture and cytology results.

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04048.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe material properties of the accessesory ligament of the deep digital flexor tendon (AL) of 21 forelimbs from horses between ages one day and 15 years were determined. The force (634–11416 N), failure stress (45–138 N/mm2), failure strain (7–24%) and tangent modulus (33–1639 MPa) are presented in relation to age. Tangent modulus did not indicate changes in elasticity due to age. The results demonstrate that complete ligament failures (CLF) of ALs of older horses (mean 7835 N) occur at lower forces than ALs of young adult horses (mean 8894 N). Sudden decreases, ‘dips’, in the force‐time curves were noticed in ligaments from foals and yearlings and in ligaments from horses>10 years. They were interpreted as the failure of a number of fibres which either fail at lower forces or are subject to higher forces than the rest. These differences in mechanical properties could be the result of age related differences in the material properties of ALs of older horses similar to alterations in collagenous tissue in other species. When analysing the data of the proximal, middle and distal regions of the ligaments separately, higher strain and elasticity were found in the distal compared to the proximal parts.It is suggested that the clinical occurrence of desmitis of the AL of older horses could be due to fibrillar failure caused by differences in the material properties of

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04049.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryFifty‐two animals, comprising 22 Irish Draught crosses (Group A), 15 Thoroughbreds (Group B) and 15 ponies (Group C) were examined ultrasonographically using a 7.5 mHz linear array probe and stand‐off pad. All animals were free of tendon disease as determined from clinical and ultrasonographical examination. The superficial (SDFT) and deep (DDFT) digital flexor tendons were scanned at 7 transverse (axial) levels between the carpus and metacarpophalangeal joint. Each transverse image was digitised using a commercially available frame grabber and the cross‐sectional areas of each tendon at each level measured using a dedicated software application.Excellent accuracy (averaging less than 5%) was demonstrated between the ultrasound generated areas and those measured from the tendonspost mortemin 12 limbs.The mean, s.d. and tolerance intervals of both SDFT and DDFT cross‐sectional areas at each level were determined for each group of horses. There was no statistically significant difference betweenGroups AandBand these 2 groups were, therefore, combined for further analysis. The cross‐sectional areas of both tendons were statistically smaller forGroup Cwhen compared toGroups AandB.The ratio of SDFT to DDFT cross‐sectional areas was calculated for each level and this demonstrated less variation between groups.The difference in measurements between limbs of the same horse was analysed. The mean differences for all groups were 9.13 mm2for the SDFT and 11.64 mm2for the DDFT. Upper limits (95% of the population) were 22.67 mm2(SDFT) and 29.22 mm2(DDFT).Weight (Groups AandC), height and mid‐metacarpal circumference (all groups) were measured and these physical parameters related to the tendon size at each level forGroups AandBcombined andGroup C.Tolerance limits and normograms were calculated. No significant regression was found for the horse group over the range of physical parameters measured while regression was shown for the ponies.The cross‐sectional areas measured in this study may be useful for determining increased tendon size in cases of bilateral tendonitis or where there is minimal disruption to the internal ultrasonographic architectur

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04050.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryTwelve adult ponies and 2 conventional foals were exposed to 106.6TCID50of Equid herpesvirus‐1 (EHV‐1), strain Ab4 and samples of respiratory tract tissues were recovered. Infectious virus in tissue homogenates was detected using susceptible cell monolayers and expression of viral antigens was monitored using indirect immunoperoxidase histochemistry of paraffin sections. The results illustrated the rapid dissemination of EHV‐1 throughout the respiratory tract, with early replication in the lungs one day after exposure. Endothelial cell infection was prominent in all areas of the nasopharynx by Day 4 emphasising the role of endotheliotropism and viraemia in dissemination of this virus to sites of secondary replication. Clinical disease in the adult ponies was

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04051.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryTwelve adult ponies and 2 conventional foals were exposed intranasal to EHV‐1, strain Ab4 (TCID5010−6.6) and samples of respiratory tract associated lymphoid tissues were recovered between 12 h and 13 days after infection. Infectious virus was detected in tissue homogenates using susceptible cell monolayers and expression of viral antigens was monitored using indirect immunoperoxidase histochemistry on paraffin sections. The results showed both infectious EHV‐1 and viral antigens in respiratory tract associated lymph nodes 12 h after exposure. Infected leucocytes were identified morphologically as lymphocytes, monocytes, macrophages and plasma cells. The rapid intracellular localisation of EHV‐1 in lymph nodes implies that cell mediated immunity is an important aspect of the equine response to thi

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1994.tb04052.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY